When talking about dream stability, lucid dreams and non-lucid dreams are completely different cases. In a non-lucid dream, all sorts of things can happen, such as extreme fear, disorientation, and excitement, without waking us up, though they could rip a lucid dream apart. Lucid dreams seem to be inherently less stable, so it takes less to throw them off balance and result in waking us up. Especiallly when first learning to controll lucid dreams, it is quite easy to become too excited and wake yourself up. Withh practice, you'll be able to stabilize your dream. This may initially entail supressing the emotion which lead to destabilization, but the end goal is to maintain focus on keeping the dream stable and keeping it lucid.